The present invention relates to monocapped bisphenol salts which can be used to make bisphenol dimers, such as bisphenol formal dimers. More particularly, the present invention relates to the use of dihydropyran as a capping agent for bisphenols and the separation of the monocapped bisphenol as a phenoxide salt from the dicapped material.
Prior to the present invention, dihydropyran was used with monophenols as a protective group, McOmie, Protective Groups In Organic Chemistry, Plenum Press, New York, 1973. It has also been found that dihydropyran can be used as a capping agent for bisphenols which are dissolved in an anhydrous ether and utilized with a condensation agent, such as toluene sulfonic acid. It would be desirable to be able to make monocapped bisphenols in the presence of bicapped bisphenols and readily separate these dihydropyran bisphenol reaction products from each other.
The present invention is based on the discovery that monocapped bisphenol salts of the formula ##STR1## can be made by effecting reaction between 0.5 to 1.0 moles of dihydropyran per mole of a bisphenol of the formula, EQU H--O--R--O--H (2)
in the presence of an organic solvent and a condensation catalyst, and thereafter forming the monocapped bisphenol salts of formula (1) by adding an alkali metal base to the reaction mixture to effect the precipitation of the monocapped bisphenol salt from the mixture.
There is provided by the present invention, a method for making a monocapped bisphenoxide salt of formula (1) which comprises
(1) effecting contact at temperatures of from 0.degree. C. to 100.degree. C. under substantially anhydrous conditions between a bisphenol of formula (2), and from about 0.5 to about 1 mole of dihydropyran per mole of the bisphenol in the presence of a condensation catalyst and an organic solvent, PA0 (2) stirring a mixture comprising the resulting bisphenol condensation product of (1) and more than 1 equivalent of alkali metal or alkali metal ion per equivalent of nuclear bound hydroxy radical of the bisphenol condensation product and PA0 (3) recovering the resulting phenoxide salt as a solid from the mixture of (2), PA0 2,2-bis-(2-hydroxyphenyl)propane; PA0 2,4'-dihydroxydiphenylmethane; PA0 bis-(2-hydroxyphenyl)-methane; PA0 2,2-bis-(4-hydroxyphenyl)-propane, hereinafter identified as "bisphenol-A" or "BPA"; PA0 1,1-bis-(4-hydroxyphenyl)-ethane; PA0 1,1-bis-(4-hydroxyphenyl)-propane; PA0 2,2-bis-(4-hydroxyphenyl)-pentane; PA0 3,3-bis-(4-hydroxyphenyl)-pentane; PA0 4,4'-dihydroxybiphenyl; PA0 4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl; PA0 2,4'-dihydroxybenzophenone; PA0 4,4'-dihydroxydiphenylsulfone; PA0 2,4'-dihydroxydiphenylsulfone; PA0 4,4'-dihydroxydiphenyl sulfoxide; PA0 4,4'-dihydroxydiphenyl sulfide; etc.
where R is a C.sub.(6-30) divalent organic radical and M is an alkali metal ion.
The divalent aromatic organic radicals included by R of formulas (1) and (2) are C.sub.(6-13) divalent aromatic hydrocarbon radicals and halogenated derivatives thereof, and divalent organic radicals of the formula, EQU --R.sup.1 --Q--R.sup.1 --,
where R.sup.1 is selected from divalent C.sub.(6-13) aromatic hydrocarbon radicals and halogenated derivatives thereof and Q is selected from --O--, --S--, --Si--, ##STR2## fluorenyl, cyclohexyl, and --C.sub.y H.sub.2y --,
where y is an integer having a value of from 1-5 inclusive.
There are included within the bisphenols of formula (2)
Alkali metal bases which can be used to form the alkali metal salts of formula (1) are, for example, alkali metal hydroxides, such as sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.; alkali metal such as sodium, potassium, lithium, etc.; ammonium hydroxide, rubidium hydroxide, cesium, hydroxide, etc. Condensation catalysts which can be employed to produce the bisphenol dihydropyran reaction products are, for example, toluene sulfonic acid, methane sulfonic acid, acidic ion exchange resins, anhydrous HCl, HBr or H.sub.2 SO.sub.4. In addition to diethylether, there also can be used as organic solvents tetrahydrofuran, dioxan, 1,2-dimethoxyethane, acetonitrile.
In the practice of the invention the monocapped bisphenol salt of formula (1) can be made by initially forming a dihydropyran reaction product of the bisphenol by effecting contact between the bisphenol and the dihydropyran in the presence of a condensation catalyst and an organic solvent. It has been found that the initial condensation reaction is exothermic and the mixture can be refluxed for an additional 0.5 to 1 hour or more after the addition has been completed. Experience has shown that the dicapped bisphenol product formed during the condensation step can be recycled to produce additional monocapped product by heating the dicapped material in the presence of additional bisphenol and condensation catalyst to effect a redistribution.
In the practice of the invention, the monocapped bisphenol salt can be made by effecting reaction between dihydropyran and a bisphenol within the scope of formula (2) in the presence of a condensation catalyst and an organic solvent. The order of addition of the various reactants is not critical and the condensation reaction is preferably achieved under reflux conditions, although a temperature of between 0.degree. C. to 100.degree. C. can be employed.
The addition of the alkali metal base can be achieved by adding the base to the condensation reaction mixture while it is being agitated which will result in the formation of the monocapped bisphenol salt as a precipitate. The addition of the alkali metal base can be continued until no further precipitation occurs. Recovery of the monocapped bisphenol salt can be achieved in accordance with standard filtration techniques facilitated by washing of the precipitate with additional organic solvent, followed by drying. It has been found that the monocapped bisphenol salt is often recovered in the form of a hydrate such as trihydrate.
The monocapped bisphenol salts of the present invention can be used as intermediates for making bisphenol dimers as shown in my copending application RD-10328, filed concurrently herewith and assigned to the same assignee as the present invention.